There are clear distinctions between our states of wake and sleep – and that is no accident, Francesca Siclari, a sleep research doctor at the Lausanne University Hospital, tells BBC News.
She says that people suffering from sleep disorders, such as narcolepsy, can find it difficult to tell the difference between their waking and sleeping lives, and this can leave them feeling confused and embarrassed.
“Someone who asks me the question of why they can’t remember their dreams, I say it’s because they fall asleep too fast, sleep too soundly and wake up with their alarm clock,” says Harvard Medical School sleep researcher Robert Stickgold. “And their response is usually, ‘How did you know that?’”
Stickgold says that a lot of people remember their dreams from a sleep onset period, when the mind starts wandering and dreamlike imagery occurs as people drift in and out of sleep – a process called “hypnagogic dreaming.”